Non-volatile memory devices are used in a wide range of applications where a power supply may not always be available. For example, non-volatile memory devices are sometimes used to store data in cellular telephones, smart cards, and personal computers. One type of non-volatile memory device is referred to as a split-gate non-volatile memory an example of which is illustrated in FIG. 1. In operation, the split-gate memory cell can be programmed with data by transferring charge to a floating gate 6 using hot carrier injection as indicated by arrow 1 in FIG. 1. The split-gate memory cell can be erased by discharging the stored charge from the floating gate 6 via a control gate 5 as indicated by arrow 2. Once the split-gate memory cell is programmed or erased as desired, the data stored in the split-gate memory cell can be accessed by reading the split-gate memory cell.
As shown in FIG. 1, a conventional split-gate memory cell can be formed in conjunction with an opposing split-gate memory cell where both opposing split-gate memory cells are arranged in a common source configuration. In particular, a common source region 4 can be electrically coupled to separate opposing drain regions 3 via each of the opposing split-gate memory cells. In operation, the common source 4 can be electrically coupled to either of the drain regions 3 by applying the appropriate voltages to the respective floating gate 6 and control gate 5 included in each of the opposing split-gate memory cells.
It is known that split-gate memory cells provide several advantages over other types of non-volatile memories, such as low programming current, low interference, as well as high speed. Split-gate memory cells can also carry several disadvantages such as relatively large size compared to other types of non-volatile memory cells.
It is also known that if the distance (D1 and D2) that the control gate overlaps the active area excessively varies from cell-to-cell, the amount of current generated in the different memory cells may vary enough that memory cells may not operate predictably. The following references discuss several types of split-gate memory cells as well as different approaches to the formation thereof: U.S. Pat. No. 4,328,565, U.S. Pat. No. 4,616,340, U.S. Pat. No. 4,783,766, U.S. Pat. No. 5,291,439, U.S. Pat. No. 5,317,179, U.S. Pat. No. 5,341,342, U.S. Pat. No. 5,373,465, 2000-75049 (Korea File: December, 2000: SEC B), and U.S. Pat. No. 6,727,545.
Notwithstanding the various approaches discussed above and in the listed references, there remains a need for improvement in the formation of split-gate memory cells and related devices.